Grub chainloading | Ubuntu -> RHEL

40_custom

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.
#
# replace <ESP_UUID> with the UUID of your ESP partition
# run 'sudo update-grub -o /boot/efi/EFI/ubuntu/grub.cfg'
menuentry "Chainload RHEL" {

	if [ x$feature_platform_search_hint = xy ]; then
		search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt1 --hint-efi=hd0,gpt1 --hint-baremetal=ahci0,gpt1  <ESP_UUID>
	else
		search --no-floppy --fs-uuid --set=root <ESP_UUID>
	fi

	chainloader /EFI/redhat/grubx64.efi
}